<template>
    <div>
      <!--banner图的返回按钮-->
      <router-link tag="div" to="/" v-show="showAbs" class="header-abs">
        <div class="iconfont iconfanhui header-abs-back"></div>
      </router-link>
      <!--banner图上方的头部信息-->
      <div class="header-fixed" v-show="!showAbs" v-bind:style="opacityStyle">
        <router-link to="/">
          <div class="iconfont header-fixed-back">&#xe624;</div>
        </router-link>
        景点详情
      </div>
    </div>
</template>

<script>
    export default {
        name: "DetailHeader",
        data () {
          return {
            showAbs: true,
            opacityStyle: {//渐隐渐现
              opacity: 0
            }
          }
        },
        methods: {//定义这个显示与隐藏 和 渐隐渐现的方法
          handleScroll () {
            console.log(document.documentElement.scrollTop)
            const top = document.documentElement.scrollTop
            if (top > 60) {
              let opacity = top / 140
              opacity = opacity > 1 ? 1 : opacity
              this.opacityStyle = { opacity }
              this.showAbs = false
            } else {
              this.showAbs = true
            }
          }
        },

        activated () {// 页面展示时 去触发的事件
          //对全局事件的绑定
          window.addEventListener('scroll', this.handleScroll)
        },
        deactivated () { // 页面即将替换成新的页面时发生
          //对全局事件的解绑
          window.removeEventListener('scroll', this.handleScroll)
        }
      /*mounted () {
        window.addEventListener('scroll', this.handleScroll)
      },*/
    }
</script>

<style lang="stylus" scoped>
  @import '~styles/varibles.styl'
  .header-abs
    position: absolute
    left: .2rem
    top: .2rem
    width: .8rem
    height: .8rem
    line-height: .8rem
    border-radius: .4rem
    text-align: center
    background: rgba(0, 0, 0, .8)
    .header-abs-back
      color: #fff
      font-size: .4rem
  .header-fixed
    z-index: 2
    position: fixed
    top: 0
    left: 0
    right: 0
    height: $headerHeight
    line-height: $headerHeight
    text-align: center
    color: #fff
    background: $bgColor
    font-size: .32rem
    .header-fixed-back
      position: absolute
      top: 0
      left: 0
      width: .64rem
      text-align: center
      font-size: .4rem
      color: #fff
</style>

